High speed multi-bending machine

ABSTRACT

A machine for forming a series of bends in a rectilinear workpiece having a formed cross-section and of predetermined length where the bends are formed at predetermined locations, at high speed, and without the aid of a machine operator. The machine contains means for positioning the workpiece, means for automatically placing a pair of movable bending dies in operative relation to first positions near the ends of the workpiece, means for operating the dies to form a first pair of bends in the workpiece, means for automatically placing the bending dies in operative relation to second positions further toward the center of the workpiece, means for operating the dies to form a second pair of bends in the workpiece, and means for discharging the workpiece and returning the bending dies to a starting position.

United States Patent lBrauer HIGH SPEED MULTI-BENDING MACHINE [75]Inventor: E. Henry Brauer, Cleveland, Ohio [73] Assignee: The Cyril BathCompany, Solon,

Ohio

[22 Filed: Aug. 18, 1972 211 Appl. No.: 281,635

11] 3,805,576 [451 Apr. 23, 1974 Primary ExaminerLowell A. LarsonAttorney, Agent, or Firm-Alan N. McCartney [57] ABSTRACT A machine forforming a series ofbends in a rectilinear workpiece having a formedcross-section and of predetermined length where the bends are formed atpredetermined locations, at high speed, and without the aid of a machineoperator. The machine contains means for positioning the workpiece,means for automatically placing a pair of movable bending dies inopera'tive relation to first positions near the ends of the workpiece,means for operating the dies to form a first pair of bends in theworkpiece, means for automatically placing the bending dies in operativerelation to second positions further toward the center of the workpiece,means for operating the dies to form a second pair of bends in theworkpiece, and means for discharging the workpiece and returning thebending dies to a startingposition.

7 Claims, '28 Drawing Figures PATENTEDAFR 23 m4 SHEET [11 [1F 10PATENTEDAPRZB 1914 3.805576 SHEET 02 0F 10 WJUM ATENTED APR 2 3 i974SHEET 0M 0F 10 MTENTEDAPR 23 I974 sum 08 HF 1o PATENTED APR 2 3 I974SHEET [19 [1F 10 WNGE MNGE 1 HIGH SPEED MULfII-BENDING MACHINEBACKGROUND or THE INVENTION forms the workpiece tangentially about theanvil die;

for-this reason, these machines are known-as tangent benders.

It is already'known to manually place a workpiece in a tangent bendingmachine and cause co-operating dies to move into operative positionthere against and form a bend in the workpiece. There are also machineswherein after the first bend is formed the workpiece may be moved in themachine and a second bend formed. These machines may take the form ofreleasable bending dies that permit the workpiece to be manuallyre-positioned with respect to the die or the form where the dies aremounted on a movable carriage that traverses the length of the workpiecefor performing bending operations therealong. In all of these machines,an operator is required to be present to load the workpiece into themachine, position the bending dies at the first bending station,energize the bending dies, release the dies, re-position the workpiece,etc. to unloading the machine. This.situation is acceptable where a fewpieces are bent; however, where large volume production is involved, theloading, unloading, and manual positioning of the bending dies reducesoutput while the continual presence of the operator raises manufacturingcosts.

This invention comprises a tangent bending machine constructed such thatvirtually all the steps are performed automatically and rapidly. Themachine con tains means for loading a workpiece ontoa work surface andmeans for forming a series of bends on the workpiece automatically, athigh speed, and without the aid of an operator, except .to discharge.the finished product. Bending dies are mounted on. movable'car riagesthat traverse along; the workpiece and perform a series of bendingoperations according to a preset sequence set in the carriage movingmeans and in'the bending die moving means prior to. receiving the work'-piece in the machine. The operator has only to insure that the workpieceis set on the work surface; thereafter, all bending operations areperformed accurately and at high speed, thus increasing manufacturingrate and reducing costs.

SUMMARY OF THE-INVENTION A high speed machine for bending a rectilinearmetal workpiece having a constant or formed section into a variety ofconfigurations, such as into window frames and door frames for trailersand other camping vehi-- cles. The machine comprises a frame thatincludes means for positioning the workpiece on a work surface, meansfor automatically placing a pair of movable bending dies in operativerelation to first positions near' the'ends of the workpiece, means foroperating said dies to form a first pair of bends in the workpiece,means for automatically placing the bending dies in operativerelation'to second positions further toward the center of the workpiece,means for operating the dies to form a second pair of bends in theworkpiece, and means for discharging the workpiece and returning thebending dies to a starting position.

The main object of this invention is a high speed machine for formingone or more bends in a rectilinear metal workpiece. Other objectsinclude a machine for bending metal. workpieces into a variety ofdifferent bends, and'different planes, especially long workpieces; abending machine in which the feed stock may be easily loaded andunloaded; and a bending machine which is capable of automatic andsemi-automatic control.

DESCRIPTION OF THE DRAWINGS FIG. 5 is a left side view of the leftcarriage taken along the lines 5-5 in FIG. 4, .showing a workpiececlamped in the carriage.

FIG/6 is a partialsectiorial view through one of the carriages takenalong thelines 6-6 in FIG. 4.

FIG. 7 is a partial sectional view taken through the carriage drivescrew along the lines 7-7 in FIG. 4.

FIG. 8 is a sectional view of a portion of the carriage taken along thelines 8-8 in FIG. 5.

FIG. 9 is a sectional view of part of the carriage taken along the lines9-9 in FIG. 5.

FIG. 10 is a sectional view of part of thecarriage taken along the lines10-10 in FIG. 5.

FIG'.'11 is a partial sectional view of the carriage taken alongthe'lines 11-11 in FIG. 6.

FIG. 12 is'a sectional view of part of the carriage taken along thelines 12-12 in FIG. 4.

FIG. 13 is a top view of one of the carriages showing one stage of thebending operation. I

FIG. 14 is a portion ofthe top view of the carriage of FIG. 13, showinga subsequent stage ,of the bending operation. I

FIG. 15 is a front view, partly broken away, of. the power. means forthecarriage main drive screw taken along the lines 15-15 in FIG. 3.

FIG. 16 is a sectional view of the carriage main drive power transfermechanism taken along the lines 16-16 in FIG. 15.

FIG. 17 is a sectional view of the bending machine taken along the lines17-17 in FIG. 2.

FIG. 18 is a partial view of the bending machine taken along the lines18-18 in FIG. 17.

FIG. 19 is a sectional view of part of the center clamp means takenalong the lines 19-19 in FIG. 18.

FIG. 20' is a partial front view of the center support for the variousshafts and guide rails taken along the lines 20-20 in FIG. 17.

FIG. 21 is a sectional view of the bending machine taken along the lines21-21 in FIG. 2.

FIG. 22 is a partial view of the bending machine taken along the lines22-22 in FIG. 21.

FIG. 23 is a partial sectional view of the bending machine taken alongthe lines 23-23 in FIG. 21.

FIG. 24 is a partial sectional view of the bending machine taken alongthe lines 24-24 in FIG. 21.

FIG. 25 is a partial view of the bending machine taken along the lines25-25 in FIG. 5.

FIG. 26 is a partial sectional view of one of the carriages taken alongthe lines 26-26 in FIG. 5.

FIG. 27 is a partial view of one of the carriages taken along the lines27-27 in FIG. 26.

FIG. 28 is a partial view of the bending machine taken along the lines28-28 in FIG. 26.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawingswhere like elements are identified with like numerals throughout thetwentyeight figures, the over-all outline of one embodiment of thebending machine of this invention is shown in FIGS. 1 and 2. Itcomprises a frame, generally indicated at 1 that comprises a front wall3 and a spaced apart parallel rear wall 5, that are held assembled in afixed geometry by a welded cross plate 7. A horizontal working surface 9is formed on top of frame 1 by a channel '11, that spans substantiallythe entire width of frame 1, by cross beams 13 that extend horizontallyforward in cantilever fashion from vertical stanchions 15, located tothe rear of frame 1, to above rear wall 5, and by the top surfaces 16aand 16b of traversable carriages that will be described in more detaillater. Mounted on top of channel 11 is a beveled strip 17 which supportsa bent workpiece during subsequent bending operations.

Along the upper edge of front plate 3 and rear plate is a track 19 thatspans the width of frame 1 and slidingly receives thereon means 20 forautomatically placing a pair of movable bending dies in operativerelation to first positions near the ends of the workpiece. As shownhere, means 20 comprises a pair of die-carrying carriages 21a and 21bfor movement along the single path defined by track 19.

Carriages 21a and 21b are independently propelled along track 19 bymeans 22 for automatically placing the bending dies in operativerelation to second positions further toward the center of the workpiecethat comprises opposed drive screws 23a and 23b that are rotatablymounted on cross plate 7, each of which is mounted in one-half the widthof frame 1. Drive screws 23a and 23b are powered at their respectiveoutboard ends by a variable speed power means 25a and 25b. Drive screw23a propels carriage 21a through complimental reception thereof with athreaded nut 27 fixed to the carriage. Power means 25a comprises a motor29 and gear reducer 31 combination that is engaged to drive screw 23athrough a conventional dual pulley wheel drive belt arrangement 33.Power means 250 is housed in a dust cover 35, that is located near theouter end of frame 1. Means 22 may also comprise other recognized drivemechanisms such as cylinder and piston drive, i.e., a fixed cylinderhaving a reciprocally mounted piston rod therein that is fastened to thecarriage. Other operable drives include a rack and pinion, i.e., amounted rack actuated by a driven pinion, etc.

ship with track 19 through bushing pads 39 that reduce friction therebetween during movement of the carriage. A main carriage support plate41, offset at 42, spans track 19 and extends both forward of frame 1 andvertical to work surface 9 and forms the support to which most of thecarriage components are mounted. A flat top plate 40 is mounted on thetop of main carriage support plate 41 containing top surface 16a thatforms a part of work surface 9. A rear wall plate 46 spans the back sideof carriage 21a parallel to and above rear wall 5.

An anvil die 43 is pivotally mounted on main carriage support plate 41on a vertical pivot shaft 45 that is in turn mounted in bearings 47attached to plate 41. Anvil die 43 has offsetcurvilinear (preferablycylindrical) faces 42a and 42b formed by a lobe-shaped work surface 49in elevational alignment with work surface 9. Die 43 is made up of aplurality of disks; shown in FIG. 6 are three disks, a hold-down disk44a, a web receiving disk 44b, and a spacer disk 440. A recess 51 isformed between disks 44a and 44b at a level, controlled by spacer disk44c, that matches the height above work surface 9 of the one or morewebs or flanges of the workpiece that are to be on the inside of thebend. Thus, work surface 49 is in alignment with work surface 9 and isadapted to receive the workpiece in a predetermined manner. Recess 51 isonly formed on one side of die 43, in offset curvilinear face 42b. Thus,rotation of die 43 will cause the workpiece to be expelled from recess51 thereby freeing carriage 23 for subsequent movement to anotherbending location. I

Work surface 49 and offset curvilinear face 42b of anvil die 43 define abending surface about which the metal workpiece is bent in thehorizontal plane. As can best be seen in FIGS. 13 and 14, anvil die 43is rotated until work surface 49 and the enclosed recess 51 engage oneor more flangesof the workpiece. Upon completion of the bendingoperation, anvil die 43 is rotated in the direction of the arrow so thatwork surface 49 is moved out of contact with the flange of theworkpiece, thus expelling the piece from anvil die 43.

Spaced from anvil die 43 on the opposite side of the workpiece isretractable clamp 55. Clamp 55 is slidingly mounted on carriage 21a bycomplimental engagement with a rail 57 that is mounted atop supportplate 41. Clamp 55 comprises a clamping jaw 59 that contains a recess 61for receiving a workpiece in a predetermined manner, a clamp jaw slideblock 63 that is in complimental sliding engagement with rail 57, and areciprocating first power means 65 that is anchored to support plate 41through a threaded connector 67. First power means 65 comprises ahydraulic cylinder 69 cimplimentally engaged to rail 57 and anchored toconnector 67, whose piston rod 71 is connected to sliding block 63. Ascan be seen in FIGS. 13 and 14, upon energization of first power means65, clamp 55 contacts the workpiece such that clamp jaw 59 receives oneor more of the workpieces webs or flanges in recess 61 and thereafterpresses the workpiece tangentially against anvil die 43 and into recess51. The contact point of the workpiece with clamp 55 and anvil die 43 isahead of the wiping die so that bending is not interfered with by clamp55.

A gate 73 is pivotedly supported slightly offset (FIGS. 9 and 10) oncarriage 21 by pivot shaft 45, support block 76, and offset ears 77a and77b and bushings 79, for curvilinear movement through a horizontal areabout shaft 45 and has a wiping die 75 mounted thereon for receiving andbending the workpiece about anvil die 43 in a horizontal plane.

Wiping die 75 slidingly mounted on edge 73 by complimental engagementwith a rail 81 that is mounted atop gate 73, comprises a die jaw 83 madeof hardened metal that contains a recess 85 similar to and aligned withrecess 61 for receiving the workpiece in a predetermined manner, a jawslide block 87 that is in complimental sliding engagement with rail 81and a reciprocating second power means 89 that is anchored to gate 73through a threaded connector 91. Second power means 89 comprises ahydraulic cylinder 93 pivotally mounted to a base 95, also slidinglyengaged to rail 81, whose piston rod 97 is connected to slide block 87by a multiplelink connection 99. Upon energization of second power means89, die jaw 83 advances toward anvil die 43 and slidingly clasps theworkpiece there between upon full, rigid extension of linkage 99.Optionally, clamp 55 presses againstthe workpiece and abuts theworkpiece against anvil die 43. Thereafter, gate 73 is swung about anvildie 43 to bend the workpiece about said die. During this swingingmotion, wiping die jaw 83 slides along the workpiece and deforms itabout anvil die 43 to form the bend. Because the exposed flanges andwebsof the workpiece are retained in recessesSl and 61 during this bendingmeovement, there is no buckling or folding of the metal.

Gate 73 is caused tomove about anvil die 43 by a means 101 for operatingthe dies to form bends in the workpiece that comprises a hydrauliccylinder 103 pivotedly mounted on parallel wing plates 104a and 104b inspaced relation to carriage 21 having its piston rod l05 connect'ed togate 73 through an eccentric arm and adjustable linkage 107. Retractionof piston rod 105 into hydraulic cylinder 103 causes pivotal motion ofgate 73 about pivot shaft 45.

As shown in FIG. 8, a protractor face 100 is on pivot shaft 45 betweentop plate 40 and gate 73 so that the operator may visually check thedegree of bend given the workpiece bywiping die 75 andadjust third powermeans 101 to increase or decrease the amount of bend. I Y

Following completion of the bending operation, which may take the formof overbending to compensate fotfspring-back of the particular metalworkpiece (shown in FIG. 14 in dotted lines), wiping die 75 is retractedfrom the workpiece and gate 73 is swung back to its original positionadjacent clamp 55. Also, anvil die 43 is rotated out of overlappingengagement with the exposed flange or flanges of the workpiece byrelease means 109 that, according to the embodiment shown in FIGS. 6 and11, comprises a pinion 111 on pivot shaft 45 that is in complimentalengagement with a rack 113 that is connected to a reciprocating pistonrod and hydraulic cylinder 115. Another embodiment of means 109 mayinclude a swing arm connecting piston rod and cylinder 115 to shaft 45to move it laterally through an arc and out of contact with theworkpiece. Carriage 21a is programmed to move along track 19 byenergizing variable speed power means 25a and drive.

screw 23a to co-act with nut 27 mounted on carriage 21a and propel thecarriage to a new bending location along horizontal work surface 9.

The places along horizontal work surface 9 where carriage 21a stops tobegin a bending operation are controlled by pre-settable programmingmeans. One embodiment thereof comprises a series (FIGS. 25 and mounted26) of actuators 117 mounted on slide blocks 119, which are in threadedengagement with a series of guide rods 120 and horizontal positioningscrews 121 arranged in parallel along the rear of frame 1 adjacent rearwall 5. On rear wall 5 of carriage 21 are mounted a series of limitswitches 123 whose roller-ended arms 125 engage actuators 1 17 to startor stop certain operations of the machine such as carriage positioning,bending, etc. As shown in FIGS. 20 and'25, positioning screws 121 arejournaled in vertical supports 127; the outboard end of the screwsextending into drive box control unit 129 wherein they are turned byhandwheels 131 to position slide blocks 119 therealong. FIG; 27 shows atypical arrangement of limit switches 123 and their respectiveroller-ended arms 125 on carriage rear wall 46. FIG. 28 shows a close-upview of a typical slide block 119 on guide rods 120 and in complimentalthreaded engagement with one positioning screw 121. Screw 121 is shownin engagement with block 119 through a nut 122 threaded on screw 121 andfixed to block 119. The other positioning screw 121 passes completelythrough block 119 without contact so that it may be used to positionanother slide block spaced apart from the block shown. Thus, there is nointerference by positioning screws that pass through slide blocks 119.

Another embodiment of the pre-settable programming means comprises ameans for controlling the rotation of drive screw 23a through a countersystem. The length of carriagetravel may be measured by the pitch of thethreads of drive screw 23a and the number of rotations of screw 23a. Bycombining a rotation counter with a memory system, the travel ofcarriage 21a may be controlled to stop at locations along the workpiecewherebends are to be made, await the completion of the bendingoperations, proceed to the next bending location, etc. This embodimentmay be housed in a small panel at one end of the drive screw and wouldeliminate the use of a plurality of actuators and slide blocks thatmayrequire frequent cleaning and other maintenance.

Shown in FIGS. 17, 18, andl9 is a means 172 for clamping or restrainingthe workpiece on work surface 9. In this particularembodiment, the meanscomprises a horizontal member supported on a vertical stanchion 167,fastened to frame front wall 3, that has a horizontal edge 169substantially perpendicular to channel 11 so that it forms part of worksurface 9. Edge 169 terminates at one end at a fixed upwardly extendingclamp side 171 and at the other end with a movable upwardly extendingclamp side 173. Movable clamp side 173 is mounted on a slideblock 175that is complimentally and slidingly received on a horizontal rail 177that extends from edge 169. Slide block 175 is connected to a powermeans 179 that comprises a hydraulic cylinder 181 and a piston rod 183;rod 183 is connected to slide block 175 and cylinder 181 is mounted onhorizontal member by an adjustable connector 185.

A workpiece loaded into work'surface 9 would span edge 169. Energizingpower means 179 causes movable clamp side 173 to move toward fixed clampside 171 and clasp the workpiece on three sides; Carriages 23a and 23bmay thereafter move along the workpiece and bend it without jostling itout of precise position using the central clamping means just described.

A means for positioning the workpiece on the work surface comprises afeed stop and positioner 133,

mounted over horizontal work surface 9, and a stop arm 135 mounted on arotatable shaft 137, housed in a channel 139, that is cantilevered froma vertical base 141 that is mounted for lateral travel by drive means143 interposed base 141 and vertical stanchions 15. Drive means 143comprises a horizontal rail 145 mounted along the rear of stanchions anda drive screw 147 arranged parallel to rail 145. A C-shaped saddle 149encompasses rail 145 and screw 147 in complimental sliding relationship.A nut 151 is threaded onto screw 147 and is fixed to saddle 149. Asscrew 147 is turned by handwheel 153, base 141 is propelled traverselyalong rail 145. Feed stop 133 is adapted to be pivoted into a horizontalplane (shown in dotted lines in FIGS. 22 and 23) away from table 9 by afifth power means 155 that comprises a hydraulic cylinder 157 whosepiston rod 159 engages in eccentric arm 161 that is mounted on shaft137; said hydraulic cylinder 157 pivoted about its rearward most end 163on vertical base 141. Stop 133 is in a vertical position when piston rod159 is extended its maximum length; it may be rotated out ofperpendicularity with table 9 by causing piston rod 159 to withdraw intohydraulic cylinder 157.

The workpiece may be loaded onto work surface 9 from one end thereoffrom an extruder or other machine. The workpiece is moved forward alongsurface 9 until it strikes feed stop 133, set at a desired position.Thereafter, clamp means 172 is energized to hold the workpiece onsurface 9 while carriages 21a and 21b move into first operativepositions near the ends of the workpiece and the bending dies form bendsin the workpiece. Thereafter, the dies are retracted and the carriagesquickly move inward to form a second pair of bends on the clampedworkpiece, automatically and without the need of an operator. Four bendsneed not always be formed in the workpiece; the programming means may bepreset to form any number of bends depending upon the desiredconfiguration. Following formation of the last bends, the dies areautomatically opened and the carriages move back to their initialpositions. The anvil dies are also rotated to expel the workpiece sothat it may be discharged from the bending machine.

I claim:

1. A machine for forming a series of bends in a workpiece wherein thebends are formed at pre-determined locations at high speed and withoutthe aid of a machine operator, comprising:

a. a frame having a horizontal work surface spanning substantially theentire width thereof;

b. said frame having a horizontal track carried throughout the width ofsaid frame supporting diecarrying carriages on each end of the frame formovement along the path defined by said track;

c. a drive screw carried on said frame connected to said die-carryingcarriages and a power means for driving said drive screw to positionsaid die carrying carriages at pre-selected locations along said frameto perform said series of bends in the workpiece;

d. said die-carrying carriages each comprising a base in mating slidingrelationship with said track, said base carrying a vertical disposedcarriage support plate;

e. an anvil die pivotedly mounted on said carriage support plate on avertical pivot shaft rotatably mounted on the support plate, said anvildie forming a bending surface about which the workpiece is formed;

f. a retractable clamp slidably mounted on said carriage support platefor movement toward and away from said anvil die to position and retainsaid workpiece against said anvil die;

g. a gate pivotedly supported on said vertical pivot shaft forcurvilinear movement through a horizontal arc about said carriage shaft;

h. a wiping die slidably mounted on said gate;

. i. means for positioning said wiping die adjacent said anvil die;

j. means for pivotedly moving said gate and wiping die about said anvildie;

k. means for automatically placing said carriages in operative relationto first positions near the ends of the workpiece;

l. means for automatically operating said clamp, said gate, and wipingdie to form a first pair of bends in the workpiece;

m. means for automatically placing said carriages in operative relationto second positions further toward the center of the workpiece; and,

n. means for automatically operating said clamp, said gate, and wipingdie to form a second pair of bends in the workpiece about said anvildie.

2. The machine of claim 1 including means for positioning the workpieceon the work surface including a feed stop positioned over said worksurface and adapted to traverse therealong for stopping the travel of aworkpiece loaded onto said work surface from the opposite end from saidfeed stop.

3. The machine of claim 1 wherein said means for automatically placingsaid carriages in operative relation to second positions further towardthe center of the workpiece comprise a plurality of positioning screwsarranged in parallel, spaced apart relationship, and substantiallyparallel to the major axis of said work surface, at least one slidingblock in complimental threaded engagement therewith, means forrestraining said block from movement other than along the longitudinalaxis of said position screw, and switch means mounted on said carriagein spaced apart relationship to said block for pre-arranged contacttherewith during movement of said carriage along said work surface.

4. The machine of claim 1 wherein said means for automatically placingsaid carriages in operative relation to second positions further towardthe center of the workpiece comprise a counter for determining theposition of said carriage with respect to the workpiece as a function ofthe rotation of said drive screw, means for programming another positionof said carriage along the workpiece, and means for actuating said meansfor rotating said drive screw to move said carriage to the otherposition.

5. The machine of claim 1 wherein said anvil die is rotatably mountedand includes a non-workpiece contact portion for ejecting the workpiecetherefrom.

face.

l I k

1. A machine for forming a series of bends in a workpiece wherein thebends are formed at pre-determined locations at high speed and withoutthe aid of a machine operator, comprising: a. a frame having ahorizontal work surface spanning substantially the entire width thereof;b. said frame having a horizontal track carried throughout the width ofsaid frame supporting die-carrying carriages on each end of the framefor movement along the path defined by said track; c. a drive screwcarried on said frame connected to said diecarrying carriages and apower means for driving said drive screw to position said die-carryingcarriages at pre-selected locations along said frame to perform saidseries of bends in the workpiece; d. said die-carrying carriages eachcomprising a base in mating sliding relationship with said track, saidbase carrying a vertical disposed carriage support plate; e. an anvildie pivotedly mounted on said carriage support plate on a vertical pivotshaft rotatably mounted on the support plate, said anvil die forming abending surface about which the workpiece is formed; f. a retractableclamp slidably mounted on said carriage support plate for movementtoward and away from said anvil die to position and retain saidworkpiece against said anvil die; g. a gate pivotedly supported on saidvertical pivot shaft for curvilinear movement through a horizontal arcabout said carriage shaft; h. a wiping die slidably mounted on saidgate; i. means for positioning said wiping die adjacent said anvil die;j. means for pivotedly moving said gate and wiping die about said anvildie; k. means for automatically placing said carriages in operativerelation to first positions near the ends of the workpiece; l. means forautomatically operating said clamp, said gate, and wiping die to form afirst pair of bends in the workpiece; m. means for automatically placingsaid carriages in operative relation to second positions further towardthe center of the workpiece; and, n. means for automatically operatingsaid clamp, said gate, and wiping die to form a second pair of bends inthe workpiece about said anvil die.
 2. The machine of claim 1 includingmeans for positioning the workpiece on the work surface including a feedstop positioned over said work surface and adapted to traversetherealong for stopping the travel of a workpiece loaded onto said worksurface from the opposite end from said feed stop.
 3. The machine ofclaim 1 wherein said means for automatically placing said carriages inoperative relation to second positions further toward the center of theworkpiece comprise a plurality of positioning screws arranged inparallel, spaced apart relationship, and substantially parallel to themajor axis of said work surface, at least one sliding block incomplimental threaded engagement therewith, means for restraining saidblock from movement other than along the longitudinal axis of saidposition screw, and switch means mounted on said carriage in spacedapart relationship to said block for pre-arranged contact therewithduring movement of said carriage along said work surface.
 4. The machineof claim 1 wherein said means for automatically placing said carriagesin operative relation to second positions further toward the center ofthe workpiece comprise a counter for determining the position of saidcarriage with respect to the workpiece as a function of the rotation ofsaid drive screw, means for programming another position of saidcarriage along the workpiece, and means for actuating said means forrotating said drive screw to move said carriage to the other position.5. The machine of claim 1 wherein said anvil die is rotatably mountedand includes a non-workpiece contact portion for ejecting the workpiecetherefrom.
 6. The machine of claim 1 including means for rotating saidanvil die such that said working surface thereof is roTated out ofcontact with the workpiece thereby expelling the workpiece fromreception in said anvil die and freeing said carriage for subsequentmovement along said work surface to a new bending location.
 7. Themachine of claim 1 including independent means for restraining theworkpiece on the work surface.